1. Field of the Invention
The present invention relates to an inspecting method for a flexible disk for use in a photo film cassette. More particularly, the present invention relates to a flexible disk inspecting method in which an unacceptable disk in a line of producing a photo film cassette can be discovered with great efficiency.
2. Description Related to the Prior Art
U.S. Pat. No. 4,423,943 discloses a type of photo film cassette, of which a leader of unexposed photo film is precontained in the cassette shell, and advanced to an outside of the cassette shell when a spool is rotated in an unwinding direction. The spool is constituted by a spool core and two flexible disks, which are disposed on the spool core, for contact with the ends of a roll of the photo film, to render the turns of the photo film neat. In the cassette of the leader-advancing type, it is necessary to transmit rotation of the spool to the roll of the photo film. To this end, the disks of the spool are provided with respective ring-like lips formed on their periphery and projected toward one another. The ring-like lips are located to cover edges of the outermost turn of the photo film, and prevent the roll from being loosened. Such a cassette is suggested in U.S. Pat. Nos. 4,834,306, 4,848,693 (corresponding to JP-A 2-18545), U.S. Pat. No. 5,271,577 (corresponding to JP-A 3-37645), and U.S. Pat. No. 5,407,146 (corresponding to JP-A 3-37645).
To advance the leader of the photo film, it is necessary to spread both flexible disks in the vicinity of a photo film passageway, to release the ring-like lips from regulation. The disks are rotatable, and are not rotated without being deformed. The disks are formed at a sufficiently small thickness. To form disks, various methods are known: vacuum forming, air-pressure forming, vacuum/air-pressure forming in combination of those, injection molding, and the like.
In the flexible disk producing method, continuous resin sheet of a thermoplastic type having small thickness is heated. The continuous sheet is deformed for example in accordance with the vacuum/air-pressure forming. The continuous sheet is moved into punch/die sets, where a punch device and a die device cut a bearing hole and then a circular contour at each disk-like portion, to form the disks. The disks as cut out of the continuous sheet are conveyed to a line for combination with spool cores.
In punching the flexible disk out of the continuous sheet, there is possibility of occurrence of burr on the disk or sticking of deposits such as dust created by the punching. If the disk has the burr or deposits, the disk, when contained in the cassette shell, cannot be properly rotated therein. The photo film would fail to be advanced. Or else the photo film would be scratched or damaged.
There is a possibility of depositing the flexible disk on the inside of a die blade of the punch/die set upon punching the disk-like portion in the continuous sheet. If the punching operation is continued, the disk remaining deposited is overlaid on another later disk. The two overlaid disks will be accidentally mounted on the spool core and contained in the cassette shell. One of the overlaid disks would come to have a reduced inner diameter of the two-stepped dish shape, so that the photo film would not be wrapped by the disk properly. The disk would be degraded in the flexibility, and could not be deformed by the photo film, which could not be advanced.